Gas separators for well pumps



June 5, 1956 N. c. WELLS GAS sEPARAToRs FOR WELL PUMPS Filed Oct. 7,1953 nited States Patent GAS SEPARAT ORS FOR WELL PUMPS Norman C. Wells,Long Beach, Calif., assigner to Agate Corporation, Los Angeles, Calif.,a corporation of California l Application October 7, 1953, Serial No.384,729

13 Claims. (Cl. 10S-203) This invention relates to improved gasseparators for use in conjunction with well pumps.

For many years, the oil industry has sought a gas separator which iscapable of effectively and completely removing gases from the iluidilowing to a well pump. Though various types of separators haveheretofore been proposed for this purpose, none has proven capable,while submerged in the liquid within a well, of effectively removingmost or all of the gases from the well liquid ilowing to the pump, whileat the same time passing enough liquid to the pump to allow a maximumrate of production of the well. As a result, most wells havingappreciable quantities of gas or froth in their iluid have been producedat relatively slow rates.

The general object of the present invention is to provide a device whichis able to effectively separate gas from the iluid ilowing to a wellpump, and which will do so even when the well iluid takes the form of alight froth having a very high gas content. Particularly contemplated isa separator of this type which will function when completely and deeplysubmerged in the well liquid and which has a sufficiently large iluidhandling capacity to permit a conventional reciprocating pump to draw afull charge of liquid upon each stroke. A further object of theinvention is to design a separator having the above operatingcharacteristics, and yet which is structurally extremely simple and hasa minimum number of working parts.

Separating devices constructed in accordance with the invention functionon a principle which is basically different from the principles of priordevices intended for this purpose. Specifically, I have found that themost dillicult froths can be broken by producing in the separating toola column of gases, and then passing the froth or gassy well fluiddirectly through and in contact with this gas column for separation intoits liquid and gaseous constituents. Such intimate contact between thewell fluidk and the gases in the gas column causes the froth or gassyfluid to instantly break down, so that its liquid content may be takenby the pump, while the gaseous content is merely added to the gascolumn. The column gases may then be vented to the exterior of theseparator, preferably past suitable check valves, for return into thewell.

To effect the desired gas separation, I provide suitable means fordirecting the well iluid into the gas column. These means may include afluid directing baille, which may have a perforated screen-like portionacting to divide the Vfluid ilow into a plurality of individual streams,each of which is very intimately contacted and surrounded by the gasesof the gas column. The pump section may be utilized to produce a forceserving to withdraw tluid from one side of the baille in a manner suchthat fluid flows through the baille from its second side to the firstside and into an upper gas space at that first side. The baille mayextend vertically within an inner chamber of the separator, and may havea lower imperforate portion adapted to direct the fluid upwardly throughan upper perforated portion thereof. The separated liquid may bewithdrawn from the device through an outlet, typically a liquiddischarge pipe depending in the separating charnber, which outlet orpipe may communicate with the separating chamber at a location lowerthan the perforated portion of the baille, and opposite its imperforateportion.

In accordance with the teachings of my copending application Ser. No.268,258, illed January 25, 1952, on Well Pump Filters, now Patent No.2,591,887, issued April 8, 1952, the device preferably is so constructedthat the liquid level beneath the gas column is always maintained abovethe point at which the liquid outlet to the pump communicates with theseparating chamber, to thus continuously maintain a liquid seal at theliquid outlet acting to prevent discharge of gases with the liquid. Alsoas taught in that invention, the device may be constructed to positivelyprevent complete venting of all of the gases in the gas column from thedevice under any circumstances. These results may be achieved bypredetermined loading ofthe gas-venting check valves, in a mannerpositively controlling the extent of venting, and thus maintaining theliquid level within a desired range.

The above and other features and objects of the present invention willbe better understoodt from the following detailed description of thetypical embodiment illustrated in the accompanying drawing, in which:

Fig. l is a vertical section through a gas separator carried at thelower end of a conventional well pump, and shown as it appears duringthe pump upstroke, typically near the upper end of that stroke;

Fig. 2 is a view corresponding to Fig. 1 but showing the condition ofthe apparatus during the pump downstroke; and

Figs. 3 and 4 are transverse sections taken on lines 3 3 and 4 4respectively of Fig. 2.

In the drawing, I have shown at 10 a gas separating device connected tothe lower inlet end of a conventional reciprocating type well pump 11.The pump and gas separating device are shown positioned within an oilwell having the usual perforated liner 12 through which oil flows fromthe surrounding earth formation into the well. The pump includes avertically extending cylinder 13 containing a vertically reciprocablepiston 14, which acts to draw well iluid upwardly past a lower inletcheck valve 15. As will be understood, the pump is connected to thelower end of a production string, through which the pumped liquid isforced upwardly to the surface of the earth.

The device 1G is threadedly connected at 16 into the lower end of pumpbarrel 13, and acts to separate gas from the well liquid before theliquid passes upwardly into the pump and production string. r1`his gasseparating device includes an upper head 17, to the lower end of whichis threadedly connected at 1S a tubular or cylindrical verticallyextending body 19. The side wall of body 19 is preferably imperforatealong its entire vertical extent'. At its lower end, tubular body 19 isopen to provide a bottom inlet through which the well iluid may flowupwardly into the interior of the tool. If desired, the lower end ofbody 19 may be threaded, as at 2li, to allow connection of an additionaltool or inlet device to the lower end of the body if desired.

During the time that the well liquid or froth is contained within theinterior of body 19, gas separates out from the liquid or froth andrises upwardly within the body, to discharge to the exterior of thedevice 10 past a number of gas discharge or venting valves 21. Thesecheck valves may comprise spherical balls of predetermined weight,positioned within the upwardly extending portions of a number ofcircularly spaced gas discharge passages 22 formed in head 17. Each ofthe passages 22 tirst extends upwardly from a point of communicationwith the interior of body 19 at the underside of head 17, and thenextends laterally outwardly to the outside of the head for venting thegases to the exterior of the device. The check valves 21 may seatdownwardly against individual seat elements 23 mounted within thevertically extending portions of the passages 22.

Liquid is discharged from the interior of body 19 upwardly to pump 13through a liquid discharge tube 24E, which is connected into theunderside of head 17 and projects downwardly within body 19 to a loweropen inlet end 25 of the tube. The upper end of tube 24 may bethreadedly connected at 27 into head 17 at a central location, tocommunicate with a central passage 26 in the head leading upwardly tothe pump. At a location 126 beneath head 17, tube 24 may be deformedlaterally, to extend downwardly within body 19 at an eccentricallypositioned or laterally offset location adjacent one side of the wall ofbody 19. The tube is preferably imperforate between its uppermost endand its lower inlet end 25, so that liquid may flow into the tube onlyat its lower end. If desired, that lower inlet end of the tube may becut at an inclination as shown.

In ilowing from the lower inlet end of body 19 to a lower inlet end 2Sof tube 24, the well liquid must pass through a baille plate 2S, whichfunctions to greatly facilitate the separation of gas from the liquid,particularly where the gas and liquid are present primarily as a froth.This baille 28 has a main portion 29 extending vertically within body19, and extending diametrically across the interior of the body toseparate the body into two semicircular passages or chambers 32 and 33.A lower part of portion 29 of baffle 28 is imperforate, up to a point30, beyond which the baftle is perforated to pass liquid and gas througha number of apertures 31` At its lower end, baille 23 has a semicircularimperforate horizontally extending portion 131, positioned beneath thelower open end of tube 24, and semicircularly engaging the inner wall ofbody 19 to prevent fluid flow into chamber 33 except by passage throughbaffle apertures 31. At its upper end, the baille 28 has a secondhorizontally extending scmicircular portion 34 engaging the inner wallof body 19 and extending across the upper end of chamber 32, to preventthe movement of any relatively large bodies upwardly toward seatelements 23. This upper horizontal portion 34 of the baille may containapertures 31a corresponding to apertures 31 in the vertical part of thebaille.

Batlle 28 is desirably secured to and carried by discharge 24, as bywelding these parts together at 35 and 36. The baffle need not bedirectly connected to body 19, but instead is desirably held in properaxial position within body 19 merely by virtue of the attachment of thebaffle to tube 24, which in turn is threadedly connected at its upperend 27 into head 17. To assemble the device, the tube 24 and baille 28as a unit may first be threadedly connected into head 17, followingwhich body 19 may be slipped upwardly onto the outside of tube 24 andthe baille, and then threadedly connected to the head at 1S. In thiscase, the baille is formed sufciently precisely to peripherally engagethe interior of body 19 along the entire vertical extents of theopposite sides of the vertical portion 29 of the baffle, and along theentire extents of the semicircular edges of horizontal portions 131 and34 of the baille. The engagement of the edges of baille 28 with the wallof body 19 should be sulciently tight to prevent fluid passage about theedges of the baille, and particularly about its lower imperforateportions, so that the fluid in passing between chamber 32 and 33 must gothrough apertures 31 and 31a of the baille. In order to positively holdthe lower imperforate portions of baille 28 in tight peripheralengagement with the wall of body 19, the lower portion of the baflle maycarry a laterally projecting vertically extending brace member 37, whichis engageable with the wall of body 19 at a location opposite the centerof the lower portion of the baille, in a manner preventing lateralmovement of the baille and tube 24 in the body.

During the upstroke of pump piston 14, liquid is drawn into tube 24through its lower inlet end 25 for passage upwardly to the pump. As theliquid is thus drawn upwardly through tube 24, the liquid level withincharnber 33 to the left of baille 28 as seen in thc figures falls, asfor instance to the level L1 indicated in Fig. l (which represents thecondition of the apparatus at or near the end of the piston upstroke).At the same time, the liquid level within the second vertical chamber 32also falls, but at a slower rate in view of the restriction offered byapertures 31 in baille 28. The liquid level L2 in chamber 32 is thusabove liquid level L1 in chamber 32 during the piston upstroke. Byvirtue of this difference in liquid levels L1 and L2, liquid fromchamber 32 flows into chamber 33 in the form of a large number ofstreams passing through apertures 31 in the baille. Such injection ofthese streams of liquid into the upper gas space within chamber 33 at alocation above the liquid level in chamber 33 necessitates passage ofthe liquid streams directly through the upper gas area, `and theresultant intimate contact of the liquid with the gas greatly enhancesseparation of any contained gas from the liquid, to maximize theeffectiveness of gas separation in the device. This eflect ispartcularly desirable where the well fluid is in the form of froth, fromwhich gas is hard to separate. The Separated gas of course accumulateswithin the upper portion of body 19, while the liquid passes into tube24 for delivery to the pump.

During the pump downstroke, the accumulated gas within the upperinterior of body 19 is vented to the exterior of the body past checkvalves 21 as a result of the difference between the hydrostatic pressureof the lluid and gas column in the body 19 and the hydrostatic pressureof the corresponding portion of the column at the outside of the body.At the same time, this difference in hydrostatic pressure causes theliquid or froth level within body 19 to rise, both within charnber 32and chamber 33, typically to the levels indicated in Fig. 2. The deviceis then ready for a subsequent piston upstroke, to repeat the cycle ofoperations already described.

In the particular form of the invention shown in the drawing, theapertures 31 and 31a in baille 28 are desirably sufliciently small thatthe restriction to fluid flow therethrough is great enough to assure theattainment of a substantial difference in the liquid levels L1 and L2 inchambers 33 and 32 respectively during the piston upstroke. At the sametime, the combined area of the apertures should be great enough toenable the device to pass relatively large quantities of liquid to thepump. For best operating results, I find it desirable to form theapertures 31 and 31a of a diameter between about M3" and 3/8, preferablyabout 1A", with the centers of the apertures typically being about 3%"apart.

In order to assure most effective separation of gas from the liquid orfroth in the present device, I find it highly desirable to predeterminethe degree of loading of gas venting check valves 21 in accordance withthe teachings of my copending application Serial No. 268,258, filedJanuary 25, 1952, on Well Pump Filters, now Patent No. 2,591,887, issuedApril 8, 1952. This predetermination of the loading of the check valvesmay be effected by merely controlling the weights of the check` valvesand their areas subjected to pressure. These valves may in the firstplace be so designed as to resist opening movement to an extentpreventing complete discharge of all of the gas from body 19 under anyoperating circumstances, or in other words assuring maintenance of acolumnA of uncxpelled gas in the upper portion of the chamber at alltimes. The presence of such a gas column above the liquid invbod'y' 19creates a liquid gas interface in the device, which in accordance withknown principles encourages a continuing separation of entrained gasfrom the liquid, and enables the passage of liquid directly through thegas space in the manner previously discussed. When a gas column ispresent above the body of liquid, any entrained gas in the liquid tendsto come to the surface of the liquid in the form of bubbles, which thenbreak at the surface (the liquid-gas interface), and thus free the gasfor entry into the gas column.

The loading of check valves 21 is also so selected as to limit theextent to which the liquid levels within the device may fall, andthereby prevent any discharge of gases to the pump with the well liquid.Specifically, the check valves, while being loaded sulliciently heavilyto assure continuous maintenance of a column of unexpelled gas in theAupper portion of body 19, are at the same time loaded sufficientlylightly to under all circumstances maintain the liquid level in thebody, and particularly in chamber 33, above the lower inlet opening 25of liquid discharge tube 24 (that is, above the liquid outlet leadingfrom body 19). In this way, a highly effective liquid seal is providedat the liquid outlet 25, positively preventing access of any of theseparated gases to pipe 24 leading to the pump.

With specific reference to the manner in which check valves 21 controlthe liquid level or levels in the device, it is noted that as gasesaccumulate in the upper portion of the chamber an unbalanced conditionis set up between the hydrostatic columns at the inside and outside ofthe 4body 19. This unbalanced condition evidences itself in the exertionof a diilerential pressure tending to open check valves 21. As will beunderstood, this diilerential pressure is caused by the Weight of Ianunbalanced portion of the liquid column horizontally opposite the innergas column. In designing a particular iilter, it is necessary to sodesign the check valves, baflle plate, and tube 24 that the differentialhydrostatic pressure will always reach a sufficient value to open valves21 and to vent some of the gas from body 19 before the liquid level inchamber 33 can fall to the level of liquid outlet 25. In designing thevarious parts to function in this manner within an oil well, the densityof the well lluid which produces the dillerential pressure for actuatingvalves 21 may be considered as ranging from .05 lb. per sq. in. per ft.(for oil `and gas froth) to .46 lb. per sq. in. per ft. (for saltwater). The device should be constructed to function properly in anyluid falling within this range.

For best operating results, l iind it desirable to so construct thedevice that the minimum liquid level L1 to which the liquid falls withinchamber 33 during normal operation of the apparatus is approximately atthe location of point 30 between the imperforate and perforated portionsof baille 28. The highest point to which the liquid levels may rise (seeFig. 2), as determined by the loading of valves 21, should desirably benot higher than the upper end of the baille.

While the dimensions of the various parts of the device may of course bevaried within a wide range as long as the above characteristics aremaintained, I will for the sake of completeness give below thedimensions of a particular tool which has actually been constructed andhas proven highly ellec'tive for separating gas from a light oil froth:

1. Internal diameter of body 19, 2.50 inches.

2. Vertical distance between seats of valves 21 and lower opening 25 oftube 24, 8-0" 3. Vertical distance between seats of check valves 21 andhighest liquid level at which check valves will open by hydrostaticpressure in a well containing light oil froth at the outside of the tool(density of froth .05 lb. per sq. in. per ft.) 6 inches.

4; Minimum dilerential pressurev at which check valves 21 open, 0.10 lb.per sq. in.

5. Vertical extent of baille 23, 7-0" 6. Vertical extent of lowerimperforate portion of baille,

7. Vertical extent of upper perforated portion of baille,

8. Apertures 31.and 31a of 1A" diameter, centers spaced apart andstaggered 9. Vertical spacing of point 30 on baille below seats ofvalves 2l, 5-2

l claim:

l. A gas separator comprising a body adapted to be carried beneath awell pump, said body forming a chamber through which well liquid isdirected in passing to said pump and acting to accumulate and contain anenclosed column of gases separated from the well liquid, lluid directingmeans for directing partially liquid and partially gaseous well fluidfrom the outside of said body into the gas column in said chamber tollow through said gas column so that the liquid and gaseous componentsof the well fluid are separated by contact with said gases of thecolumn, check valve means adapted to vent gases from said gas column tothe exterior of said body separately from the liquid, but preventingreverse fluid llow into the body through said check valve means, andliquid outlet means for separately discharging the liquid to said pump.

2. A gas separator as recited in claim l, in which said lirst mentionedmeans are constructed to direct a plurality of separate streams of saidwell fluid into said gas column at a plurality of different locations.

3. A gas separator as recited in claim 1, in which said lluid directingmeans comprise a screen in said chamber containing a plurality ofapertures through which said well lluid llows, said apertures beingsufficiently restricted to lluid flow therethrough to maintain differentliquid levels at opposite sides of the screen during the pump upstrokeso that iluid passing through the screen apertures from beneath theliquid level at one side enters a gas column above the liquid level atthe other side.

4. A gas separator as recited in claim l, in which said liquiddischarging means comprise a liquid outlet communicating with a lowerbody of liquid in said chamber at a location spaced beneath said valvemeans and not communicating with the chamber at any point above saidlocation, said check valve means being loaded sullciently lightly toassure maintenance of the liquid level in said chamber above said liquidoutlet location at all times during operation of the separator.

5. A gas separator as recited in claim 4, in which said valve means areloaded sulliciently heavily to prevent complete venting of the gasesfrom said chamber and to thereby at all times maintain an unventedcolumn of gases in the chamber.

6. A gas separator as recited in claim 5, in which said fluid directingmeans comprise a screen in said chamber containing a plurality ofapertures through which said well iluid flows, said apertures beingsufficiently restricted to iluid flow to maintain different liquidlevels at opposite sides thereof during the pump upstroke so that lluidpassing through the screen apertures from beneath the liquid level atone side enters a gas column above the liquid level at the other side.

7. A gas separator comprising a vertically extending hollow body adaptedto be carried beneath a well pump and through which well liquid llows inpassing to the pump, baille means in said body having a verticallyextending portion and dividing said body into first and secondvertically extending spaces, means forming an inlet for introducingpartially liquid and partially gaseous well fluid into the first of saidspaces, said body being constructed to enclose and maintain in an upperportion thereof a column of gases separated from the well liquid,

means for venting said gases from the body separately from the liquid,means forming a liquid outlet leading to the pump and communicating withthe second of said spaces at but not above an outlet location which isspaced below said venting means, and is lower than said column of gases,said baille means containing aperture means through which said liquidand gaseous fluid tlows from said first side of the baille means intothe gas column at the second side of the baille means.

S. A gas separator as recited in claim 7, in which said baille means hasan upper perforated portion and a lower iniperorate portion requiringpassage of the well lluid through the perforated portion, and saidoutlet communicates with the second side of the baille opposite saidimerforate portion thereof,

9. A gas separator as recited in claim 7, in which said liquid outletcomprises a tube extending downwardly within said body communicable atan upper end with the pump and communicating with the interior of thebody at said outlet location spaced beneath said venting means, saidventing means comprising check valve means for discharging gases from anupper portion of the body to the exterior thereof.

l0. A gas separator as recited in claim 9, in which said check valvemeans are loaded Vsufficiently heavily to at all times maintain a columnof unvented gas in the body, and being loaded sufficiently lightly to atall times maintain a liquid level above said outlet location at saidsecond side ofthe baffle means.

11. A gas Separator as recited in claim 10, in which said aperture meanscomprise a large number of apertures formed in an upper portion of saidbaille means, said bafile means having a lower imperforate portionopposite said point of communication of the liquid outlet tube with theinterior of the body and requiring passage of said fluid through saidupper apertures in owing past the baffle means.

12, A gas separator as recited in claim 9, in which said aperture meanscomprise a large number of apertures formed in an upper portion of saidbaille means, said baffle means having a lower imperforate portionopposite said point of communication of the liquid outlet tube with theinterior of the body and requiring passage of said fluid through saidupper apertures in flowing past the baille means.

13. A gas separator comprising a body adapted to be carried beneath awell pump, said body forming a chamber through which well liquid isdirected in passing to said pump and acting to accumulate and contain anenclosed column of gases separated from the well liquid, means fordirecting partially liquid and partially gaseous well fluid from theoutside of said body into the gas column in said chamber to flow throughsaid gas column so that the liquid and gaseous components of the welliluid are separated by contact with said gases of the column, vent meansfor passing gases from said gas column to the exterior of said bodyseparately from the liquid, and liquid outlet means for separatelydischarging the liquid to said pump, said tluid directing meansincluding a screen in said chamber containing a plurality of aperturesthrough which said well fluid flows from one side of the screen to theother, said apertures being sulllciently restriced to fluid ilowtherethrough to maintain different liquid levels at opposite sides ofthe screen during the pump upstroke so that fluid passing through thescreen apertures from beneath the liquid level at one side enters a gascolumn above the liquid level at the other side.

References Cited in the file of this patent UNITED STATES PATENTS

1. A GAS SEPARATOR COMPRISING A BODY ADAPTED TO BE CARRIED BENEATH AWELL PUMP, SAID BODY FORMING A CHAMBER THROUGH WHICH WELL LIQUID ISDIRECTED IN PASSING TO SAID PUMP AND ACTING TO ACCUMULATE AND CONTAIN ANENCLOSED COLUMN OF GASES SEPARATED FROM THE WELL LIQUID, FLUID DIRECTINGMEANS FOR DIRECTING PARTIALLY LIQUID AND PARTIALLY GASEOUS WELL FLUIDFROM THE OUTSIDE OF SAID BODY INTO THE GAS COLUMN IN SAID CHAMBER TOFLOW THROUGH SAID GAS COLUMN SO THAT THE LIQUID AND GASEOUS COMPONENTSOF THE WELL FLUID ARE SEPARATED BY CONTACT WITH SAID GASES OF THECOLUMN, CHECK VALVE MEANS ADAPTED TO VENT GASES FROM SAID GAS COLUMN TOTHE EXTERIOR OF SAID BODY SEPARATELY FROM THE LIQUID, BUT PREVENTINGREVERSE FLUID FLOW INTO THE BODY THROUGH SAID CHECK VALVE MEANS, ANDLIQUID OUTLET MEANS FOR SEPARATELY DISCHARGING THE LIQUID TO SAID PUMP.